Diesel engine use for passenger car applications is increasing due to the benefit of better fuel economy. Further, gasoline engines are increasing compression ratios to improve the fuel efficiency. As a result, diesel and gasoline engine accessory drive systems have to overcome the vibrations of greater magnitude from crankshafts due to above mentioned changes in engines.
Due to increased crankshaft vibration plus high acceleration/deceleration rates and high alternator inertia the engine accessory drive system is often experiencing belt chirp noise due to belt slip. This will also reduce the belt operating life.
Crankshaft isolators/decouplers and alternator decouplers/isolators have been widely used for engines with high angular vibration to filter out vibration in engine operation speed range and to also control belt chirp.
Representative of the art is WO2007121582A1 which discloses a one way isolator for high torque devices, such as alternator-starters, driven by a flexible drive means includes a hub and a sheave each of which includes at least one stop member. The hub and sheave are linked by a isolating spring and, via a bearing and/or bushing, can rotate with respect to each other to provide isolation, through the spring, from torque variations when torque is transferred from the flexible drive means to the device. When substantial amounts of torque are transferred from the device to the flexible drive means, the sheave rotates with respect to the hub to bring the stop members into contact such that the isolator then acts like a solid pulley to facilitate the transfer of the torque from the device.
What is needed is an isolating decoupler comprising a single bearing disposed between the shaft and the pulley, the bearing comprising a radial centerline, the radial centerline aligned with a mid-line of the belt bearing portion. The present invention meets this need.